The present invention is directed to a movable upper tool for the separation of die-cut blanks from a sheet which has been processed in a press that manufactures package blanks, particularly a press that manufactures corrugated cardboard blanks from a sheet.
A press that manufactures corrugated cardboard package blanks usually includes several successive stations which are in a chronological order starting with a feeding station, a die-cutting station, a waste-stripping station and a blank-separating and delivery station. In such a machine, the sheet of corrugated cardboard is introduced from the feeding station and is gripped by grippers of a conventional device which consists of a gripper bar mounted at its ends on two chain conveyors that are on the lateral sides of the frame of the machine. The sheet of corrugated cardboard, which is held in the grippers of the gripper bar, is then carried sequentially through the above-mentioned stations with a dwell at each station. With the first standstill or dwell, the sheets will be die-cut by the die-cutting station in order to die-cut blanks in the sheet, which blanks are connected to one another by bridges called nicks. Then, at a second standstill, the die-cut sheet will have waste bits removed from the sheet and, in the third station and standstill, the blanks will be separated from one another and piled up in a separating and delivery station.
With the waste bits having been removed from the sheet of corrugated cardboard in the waste-stripping station, the sheet free of waste will be carried into the blank-separating and delivery station, where the blanks will be separated from one another owing to a movement identical to the one used in the waste-stripping station.
In the known way of using a movable upper tool and a fixed lower tool in a blank-separating station, the upper tool will consist of an assembly of punches and the lower tool will consist of a matrix with apertures corresponding to the size of the blanks. The movable upper punches will push the blanks through the apertures of the lower matrix, which action causes the breaking of the various bridges which interconnect the blanks to one another. Separating tools have to be adjusted to the shape and to the disposition of the blanks of every new series of sheets to be processed. Generally, the punches are fitted in alignment with the trim-lines of the press on a base plate fixed to a movable upper tool-carrier frame of the blank-separating station. Underneath and opposite every punch is arranged a corresponding aperture or opening of a lower matrix which consist of little bars. The little bars are arranged in an overlapping manner in order to make up a grid or matrix whose openings have approximately the same dimensions as the blanks to be separated.
In order to avoid the necessity of manufacturing new tools for the separation of blanks with every new pattern of die-cut blanks in a sheet, U.S. Pat. No. 4,175,686, whose disclosure is incorporated herein by reference thereto and which claims priority from the Swiss Application resulting in Swiss Patent 617 886, suggests the mounting of punches horizontally shiftable along bars fitted on a frame which is vertically movable. Every punch has the shape of a block and is connected to its neighbor by means of a telescopic connection. A fixed lower matrix consists of interconnected bars which are shiftable so as to form a grid whose meshes or openings have adjustable dimensions to correspond to the particular blank being processed.
Another way of realizing the movable upper tool consists in using a plate provided with through-bushings in which are arranged self-locking pins which enable the fastening of punches which are designed to push the blanks to be separated through corresponding apertures in the lower tool. This solution is disclosed in U.S. Pat. No. 5,192,011, whose disclosure is incorporated herein by reference thereto, and also by Swiss Patent No. 681 874.
A third way of realizing a movable upper tool consists in using a plate with a great number of apertures, and on a lower side of the plate are mounted rigid punches for the separation of the blanks. These punches are fitted on the plate by self-adhesive strips. This is disclosed in U.S. Pat. No. 5,353,978, whose disclosure is incorporated herein by reference thereto, and by Swiss Patent 682 651.
As mentioned in U.S. Pat. No. 5,353,978, it is necessary that the movable upper tools be made in such a way that the tools allow passage for air during a vertical movement of the tool. For example, numerous apertures are in the plate which make up these tools.
This manner of obtaining the separating blocks requires a construction of a new tool, specifically for each blank configuration on the sheet and independent of the price and time implied in the realization of this new tool. An important storage space must also be incorporated for storing the various tools or punches, since they may be used in subsequent runs at a later date.
Thus, the blank-separating tools, which have just been described, have all the drawbacks of necessitating a rather long preparation, depending on every different run to be achieved by the machine. These operations diminish the performance of the machine when it is necessary to treat numerous different runs in the same working day and augments the downtime during which the machine is inoperative. Consequently, the problem to be solved consists in increasing the effective production of the machine which will manufacture the blanks for forming packages.